Generally in a vehicular headlamp, as shown in FIG. 6, a bulb insertion hole 4b for insertion of a bulb body 2b of a light source bulb 2 is formed in a reflector 4, and an annular wall 4j is formed around the bulb insertion hole 4b. A body supporting portion 2c of the light source bulb 2 is designed to abut on bulb abutment face 4k of the annular wall 4j from behind (from the exterior of annular wall 4j in the direction of bulb insertion).
However, in the conventional vehicular headlamp, as shown in FIG. 6, the body supporting portion 2c of the light source bulb 2 substantially closes the bulb insertion hole 4b of the reflector 4. Heat is radiated along with the light emitted from a light-emitting portion 2a of the light source bulb 2, and the heat tends to be trapped in an internal space of the reflector 4. Hence, a problem exists in that the reflector 4 reaches a high temperature and hence may suffer heat deformation.